Photoinitiated amino-group formation in a polymer matrix and its application to polymer surface modification

Abstract

Photochemical reactions of pendent acyloxyimino (AOI) groups in copolymers of acryloyl acetophenone oxime (AAPO) with styrene (St) or methyl methacrylate (MMA) were investigated in the solid phase AAPO(26.3)-St films with 10 wt.% benzophenone as a sensitizer were irradiated at 366 nm at room temperature under air. After irradiation alkylimino groups and double bonds were introduced into the copolymers and their yields were 68% and 29% rspectively. The alkylimino groups could be converted into amino groups by hydrolysis with water very easily. The quantum yields of photodecomposition of AOI groups and of formation of amino groups were 0.70 and 0.48 respectively. The yields of amino groups did not depend on the atmosphere employed during irradiation, irradiation wavelengths or residual casting solvents in the films, but depended on the content of AOI groups in the copolymers: the yield decreased with an increase in AOI groups. This was explained by assuming that the increase in the content of AOI groups in a polymer matrix facilitated the formation of acetophenone azine by the mutual recombination of amino radicals, which depressed the formation of alkylimino groups. This assumption was verified. It was found that when the amino groups in irradiated AAPO-St(or MMA) were changed into ammonium groups, the wettability of the copolymer surface was modified remarkably and that they made it possible for an acid dye to dye the copolymer surface.